Edit by Cola_Colin: @wondible mentioned issues with attaching files and this discussion resulted. I've put it here because it was extremely off topic orginal posts follow: for screenshots don't use PNG, png is lossless and makes the file size too big. You're safe saving to JPG with a 7 to 8 quality on the slider (in Photoshop).
It's 287kb. I've uploaded at least one over 500 before. I was also having issues putting a file on S3 the other day.
You may want to check out tools like Hyperdesktop that allow to make a partial screenshot and instant upload it to imgur, placing the link in your clipboard.
I have the same experience, the fact of the matter is it won't accept that size anymore. Mayhaps Uber are running short on HDD space?